1. Field of the Invention
The present invention relates to a power tool, such as a jigsaw or saber saw, for reciprocally driving a blade.
2. Description of the Related Art
Reciprocal-movement power tools, such as jigsaws and saber saws, cut work pieces by reciprocating a blade. When the work piece is thick, the blade needs to be reciprocated by a large movement amount to produce a large cutting force. On the other hand, when the work piece is thin, it is better to reciprocate the blade by a small movement amount. Problems arise when a power tool with a large reciprocating amount is used to cut a thin work piece. For example, the work piece can be shaken by movement the blade, the cut surfaces can be roughly cut, the work piece can bend, and the blade can break. On the other hand, problems can also arise when a reciprocal-movement power tool with a small movement amount is used to cut a thick work piece. For example, saw dust is not properly removed, clogs can occur because dust is not properly removed, the cut surfaces can be roughly cut, and the life of the blade can be shortened because the same part of the blade is always used.
Japanese Patent-Application Publication Nos. 59-176001 and 2000-225517 disclose reciprocal-movement power tools capable of mechanically changing reciprocal movement amount. However, the power tools disclosed in these publications change the reciprocal movement amount using a complicated mechanism for converting rotational movement of a motor into reciprocal movement for cutting and machining. In addition, these conversion mechanism generate a great deal of vibration and noise.